High-precision mapping reveals the structure of odor coding in the human brain

• Published in: Nature neuroscience Vol. 26; no. 9; pp. 1595 - 1602
• Main Authors: Sagar, Vivek, Shanahan, Laura K., Zelano, Christina M., Gottfried, Jay A., Kahnt, Thorsten
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.09.2023; Nature Publishing Group
• Subjects: 59/36; 631/378/2624/1704; 631/378/2649/1723; Activity patterns; Amygdala; Animal Genetics and Genomics; Behavioral Sciences; Biological Techniques; Biomedical and Life Sciences; Biomedicine; Brain; Brain mapping; Coding; Computational neuroscience; Cortex (olfactory); Functional magnetic resonance imaging; Humans; Magnetic resonance imaging; Medical imaging; Neural coding; Neurobiology; Neuroimaging; Neurosciences; Odor; Odorants; Odors; Perception; Piriform cortex; Smell
• ISSN: 1097-6256; 1546-1726; 1546-1726
• DOI: 10.1038/s41593-023-01414-4

Odor perception is inherently subjective. Previous work has shown that odorous molecules evoke distributed activity patterns in olfactory cortices, but how these patterns map on to subjective odor percepts remains unclear. In the present study, we collected neuroimaging responses to 160 odors from 3 individual subjects (18 h per subject) to probe the neural coding scheme underlying idiosyncratic odor perception. We found that activity in the orbitofrontal cortex (OFC) represents the fine-grained perceptual identity of odors over and above coarsely defined percepts, whereas this difference is less pronounced in the piriform cortex (PirC) and amygdala. Furthermore, the implementation of perceptual encoding models enabled us to predict olfactory functional magnetic resonance imaging responses to new odors, revealing that the dimensionality of the encoded perceptual spaces increases from the PirC to the OFC. Whereas encoding of lower-order dimensions generalizes across subjects, encoding of higher-order dimensions is idiosyncratic. These results provide new insights into cortical mechanisms of odor coding and suggest that subjective olfactory percepts reside in the OFC. The authors used precision functional imaging and computational modeling to uncover the structure of perceptual odor coding in the human brain. Olfactory areas differ in the granularity, dimensionality and subjectivity of perceptual coding.